Human Ancestor 'Lucy' Walked Upright 3.2 Million Years Ago

This fragment of a lower arm bone represents just one piece of the second partial skeleton of science's best-known early human ancestor. It's 400,000 years older than the famed hominid "Lucy," which is the same species, and it's male.

Credit: Yohannes Haile-Selassie, Cleveland Museum of Natural History

The discovery of a new hominid skeleton in Ethiopia shows
that the human ancestor represented by the famed "Lucy" walked on two
legs rather than moving like a knuckle dragger, researchers say.

Anthropologists have long debated whether the short-statured
female Lucy typically walked upright or not. She had represented the only
known skeleton of Australopithecusafarensis, and would have
stood at a height of 3.5 feet (about a meter) some 3.2 million years ago.

But the second partial skeleton, named "Kadanuumuu"
("big man" in the Afar language), has both the shoulders and long
legs that compare well to modern
humans, according to Yohannes Haile-Selassie, curator and head of physical
anthropology at the Cleveland Museum of Natural History in Ohio.

"It's only the second partial skeleton of A.
afarensis to be recovered; it's 400,000 years older than Lucy and it's
male," Haile-Selassie said. "But just as important, the fossil
remains provide conclusive proof that A. afarensis could walk
upright freely without the use of its hands."

Kadanuumuu lived even earlier than Lucy around 3.6 million years
ago, but would have towered over the smaller female at a height of 5 to 5.5
feet (1.5 to 1.7 m) tall. His legs and arms look proportionally similar to that
of modern humans.

The new skeleton contains most of the parts found in Lucy,
along with previously unknown pieces, such as much of the rib cage and a nearly
complete adult shoulder blade.

"Kadanuumuu's shoulder was also a major
discovery," Haile-Selassie noted. "It shows that our ancestor's
shoulder blade and rib cage were much more similar to those of modern humans
than previously had been thought."

The older, bigger brother to Lucy appears to match well with
fossilized
footprints that also date back to 3.6 million years ago in Laetoli,
Tanzania. That eastern African site shows that early
human ancestors regularly walked upright, without knuckle-dragging
impressions or unusually spread toes.

Renowned Ethiopian fossil hunter Alemayehu Asfaw found the
first part of Kadanuumuu in February 2005 at Korsi Dora, about 210 miles (nearly
340 kilometers) northeast of the Ethiopian capital Addis Ababa.

Later excavations by an international team between 2005 and
2008 turned up an upper arm,collarbone,
neck bones, ribs, pelvis, sacrum, a thighbone, a shinbone and the shoulder
blade. The discoveries came as part of the Woranso-Mille Project that has been
ongoing since 2004.

Researchers published their early findings in this week's
issue of the journal Proceedings of
the National Academy of Sciences, and hope to continue revealing more about the
skeleton officially designated KSD-VP-1/1.

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